1. Field of the Invention
The present invention relates generally to an attachment for use with an electromechanical driver device, and more specifically to a vascular expander device which is insertable, expandable, collapsible, and removable within and from a vascular, lumen, or similar vessel by means of a remote electromechanical driver device.
2. Description of the Prior Art
Upon identification of a stricture and/or stenosis in an artery, gastrointestinal tract, bowel, or other vessel of the body (for another important example, the bile duct) several treatment actions may be selected. Surgical intervention may include fully invasive procedures such as bypasses in which supplemental vessels are transplanted from other regions of the body, or in less frequent circumstances, artificial supplemental structures are implanted. This fully invasive procedure often requires significant hospitalization and tremendous rehabilitation. For these reasons, it has been a goal of the industry to minimize the number of instances in which these procedures are performed to the barest minimum. The less invasive surgical intervention, which has become more desirable, is one in which a device is inserted into the segment of the vessel which has narrowed, and to inflate the device within the segment until the passage through the vessel has been expanded to a more acceptable diameter. This procedure has been widely accepted and is only untenable in situations where the stenosis has occurred to such a great extent that the device cannot be inserted. Target tissues for such procedures, as mentioned above, include cardiovascular arteries which have sclerosed, peripheral vascular arteries which have sclerosed, bowel tissue which has narrowed due to scarring or other narrowing event, to an extent that such sclerosing or narrowing inhibits the proper flow of digestion, and normal use of any other soft tissue vessel which has sufficient elasticity to expand.
While the methodological innovation of expanding a structure within a stenosed vessel to increase flow therethrough to a more desirable level is one of the great advances in medicine of the last few decades, the instruments utilized in the execution of these procedures have lagged substantially behind the development curve. The traditional instrument for such a procedure, for example, a dilation balloon catheter for an angioplasty, is a long flexible tube having a selectively expandable volume disposed in the tip of the device. This tube having the expandable volume in its tip is directed through the femoral artery, the aorta, and into the heart itself. From the heart, it is directed into the partially blocked vessel. Once the tip of the device is disposed in the narrowed channel, a fluid (usually saline) is advanced into the flexible expanding volume to cause it to inflate. The inflating balloon presses against the walls of the vessel, causing them to expand outwardly. This process is continued until the vessel is enlarged to the point that the physician feels that the flow through it will be sufficient to alleviate the symptoms and potential for damage.
One of the most important drawbacks of the balloon catheter design is that the means for inflating the volume, and the manner in which the volume is inflated, completely blocks the flow of fluids through the vessel during the procedure. This failure is inherent in the design by virtue of the fact that the balloon must occlude the vessel in order to apply the pressure to the walls. A few alternative designs have been proposed in the art which provide a minimal solution to the problem by offering a number of cannulae, or narrow and rigid pass through holes, formed in the balloon itself, for permitting a small amount of fluid to flow when the balloon is fully inflated.
This attempted solution further highlights (and exacerbates) the other important failure of balloon type devices. This failure relates to the gathering of information about the expansion of the vessel walls. More particularly, one of the important measurements involved with any vessel expansion is the change in diameter, which is attained at a given internal pressure of the balloon. The relationship of pressure and diameter is inherently imprecise as vessel tissue varies in elasticity across the spectrum of potential patients as well as the degree of expansion or vessel narrowing which has already taken place (for example, a second or third angioplasty might proceed with a completely different pressure to diameter profile from that of a first time procedure). The inclusion of narrow passages through the expanding volume, especially in the case of a balloon having a cannulated structure, results in a very unreliable interior pressure to diameter relationship.
Unfortunately, it is also not always the case that the one time expansion of the vessel (during the surgical intervention) continues to remain effective over a long period. The stenosis of the vessel often continues, and the flow through the treated area may drop again to a level requiring additional intervention. As repeated expansion of the vessel stresses the tissue, and has been linked to the formation of aneurysms, it has been found necessary to install a permanent structural element into the vessel. These structural elements, which are generally referred to as stents, are generally tubular in shape, but are formed in a variety of different manners, including solid cylinders, meshes, fabrics, etc. The introduction of a stent into a patient usually follows a traditional angioplasty procedure, during which the vessel is expanded to the necessary diameter for the stent to be inserted. The remote installation of a stent is difficult, but several designs have been offered in which the stent is delivered in a collapsed form, and is then irreversibly expanded into position by means incorporated into the insertion tube. The diameter of a specific stent is, therefore, predetermined, and the diameter of the stent selected must be picked correctly.
It has been found, however, that over time, the stent is incorporated by the body, into the tissue wall of the vessel. Continued stenosis of the vessel around, and/or through the stent, presents an immediately understandable problem for continued treatment, i.e., the stent is a rigid metal structure which will prevent an angioplasty procedure from being able to expand the vessel (the balloon will expand against the stent, and the stent will remain undeflected).
Removal of a stent which has already been incorporated by the body is a considerable problem. Techniques of sheering off the tissue which has built up on and around the inside of the stent have been provided in the art, however, these generally include a rotating blade within the vessel. The risks of particulate matter becoming dislodged within the vessel, and causing considerable damage as a result, as well as the potential for weakening the structural integrity of the vessel walls to the point of rupture has limited the applicability of this technique. In the final analysis, stents have a tainted usefulness insofar as they may alleviate the stenosed condition for a short period, but may preordain and require a full bypass procedure if the vessel begins to re-stenose (which occurs in a vast number of such cases).
It is also a failure of the present instrumentation that as with many such devices of the prior art, all of these devices are considered fully disposable, and are, in fact, thrown away after a single use. They are complicated devices, having multiple moving parts, requiring substantial structural integrity and, therefore, expense in manufacturing. The fact that they are used only once, and no part can be used again render the use of such devices expensive and wasteful of resources.
In addition to this failure, as can be readily observed from the preceding descriptions, the prior art devices suffer from numerous other limitations, which would be desirable to overcome. These includes the requirement that the surgeon manually actuate all of the features and functions of the balloon catheter and the fact that the angioplasty balloon inflates to a discrete size, necessitating the replacement of an undersized balloon with the next size balloon. This process may be repeated numerous times until the appropriate diameter is achieved. Any and all undersized balloons are wasted during this procedure.
It is, therefore, a principal object of the present invention to provide a device which may be remotely actuated to expand and apply a radially outward pressure against the walls of a narrowed vessel or lumen in conjunction with and in accordance with a surgical procedure.
It is further an object of the present invention to provide an instrument for expanding tissue during gastrointestinal surgery, cardiovascular angioplasty, peripheral vascular angioplasty, and other procedures, which will reduce the waste of resources and facilitate a range of expansion (for example, eliminating the need for sizing the vessels as described above) by permitting use as an attachment to an electromechanical driver device.
It is further an object of the present invention to provide a device which reduces the requirements for the surgeon, gastroenterologist, or cardiologist to manually actuate different components and mechanisms.
It is further an object of the present invention to provide a device which does not occlude the vessel in which it is expanding, thereby permitting a significant flow of fluid to continue as it expands against the vessel or lumen walls.
It is further an object of the present invention that at least a portion of the expanding section of the device be selectively disengageable and implantable within the vessel or lumen if it is determined that the vessel or lumen requires a permanent structural support.
It is further an object of the present invention that the device, and in particular the portion which may be selectively permanently implanted in the vessel or lumen, be expandable through and permanently (and rigidly) expanded to a diameter within a range of different diameters.
Other objects of the present invention shall be recognized in accordance with the description thereof provided hereinbelow in the Summary of the Invention, and in the Detailed Description of Preferred Embodiments in conjunction with the Figures.
The preceding objects of the invention are provided by an attachment of the present invention which is coupled with, and actuated by, an electromechanical driver device set forth in more complete detail in U.S. Ser. No. 09/324,452, entitled xe2x80x9cAn Electromechanical Driver Device for use with Anastomosing, Stapling, and Resecting Instrumentsxe2x80x9d, assigned to the same assignee of the present invention. More particularly, the attachment may be embodied in a variety of different structures, a preferred one being set forth in more detail hereinbelow. Each embodiment of the attachment, however, is coupleable to the distal end of the flexible shaft of the electromechanical driver device which causes the attachment, among other additional functions, to expand and contract upon proper remote actuation of the electromechanical driver device and in accordance therewith.
More specifically, the electromechanical driver device comprises a handle and a flexible drive shaft. The handle has a pistol grip-styled design, having a finger trigger which is independently coupled to a motor which turns a flexible drive shaft (described more fully hereinbelow). The motor is a dual direction motor, and is coupled to a manual drive switch mounted to the top of the handle, by which the surgeon user can selectively alter the turning direction of the motor. This dual direction capacity may be most simply achieved by selecting a motor which turns in a direction corresponding to the direction of current, and actuation of the manual drive switch alters the direction of the current accordingly. In this example, the power source supplying the motor must be a direct current source, such as a battery pack (and most desirably, a rechargeable battery pack). In the event that the device should be useable with an alternating current, either a transformer can be included, or a more sophisticated intermediate gearing assembly may be provided. In conjunction with the present description, the embodiments of the present invention which will be described utilize a rechargeable battery pack providing a direct current.
In addition to the motor components, the handle may further include several other features, including: (1) a remote status indicator; (2) a shaft steering means; and (3) at least one additional electrical supply. First, the remote status indicator may comprise an LCD (or similar read out device) by which the user may gain knowledge of the position of components (for example whether the spokes are at the closed position or at a definite expanded diameter). Second, the handle also includes a manually actuateable steering means, for example, a joystick or track ball, for directing the movement of the flexible shaft (by means of steering wires implanted in the flexible shaft described more fully hereinbelow). Finally, the handle may include an additional electrical power supply and an on/off switch for selectively supplying electrical power to the attachments.
More particularly, with respect to the flexible shaft, the shaft comprises a tubular sheath, preferably formed of a simple elastomeric material which is tissue-compatible and which is sterilizable (i.e., is sufficiently rugged to withstand an autoclave). Various lengths of this flexible shaft may be provided in conjunction with the present invention. In this case, the flexible shaft and the handle should be separable. If separable, the interface between the proximal end of the flexible shaft and the distal end of the handle should include a coupling means for the drive components.
Specifically regarding the drive components of the flexible shaft, within the elastomeric tubular sheath is a smaller fixed tube which contains a flexible drive shaft which is capable of rotating within the fixed tube. The flexible drive shaft, itself, simply must be capable of translating a torque from the motor in the handle to the distal end of the flexible drive shaft, while still being flexible enough to be bent, angled, curved, etc. as the surgeon deems necessary to xe2x80x9csnakexe2x80x9d through the vessel of the patient up to the occluded section. For example, the flexible drive shaft may comprise a woven steel fiber cable. It shall be recognized that other flexible drive shafts may be suitable for this purpose.
In order to securely engage an attachment, such as the vessel and lumen expander attachment which is the subject of the present invention (as described more fully hereinbelow), it is preferred that the distal end of the flexible shaft include a stability gripping feature, which preferably is simply a set of prongs which engage a pair of recesses in the coupling end of the attachment (as described more fully hereinbelow). Further, the distal end of the flexible drive shaft must have a conformation which permits the continued translation of torque. For example, the distal end of the flexible drive shaft may be hexagonal, thereby fitting into a hexagonal recess in the coupling interface of the attachment. The distal end of the flexible drive shaft may further include additional topological features which enhance the engagement of the flexible drive shaft to a potential attachment, but which are stationary and thereby provide a stable reference position for applying the rotation to only a portion of the attachment (so that the entire attachment does not rotate when the torque is applied to one portion of the attachment).
As suggested above, in conjunction with the manually actuateable steering means mounted to the handle, the flexible shaft further includes at least two steering wires which are flexible, but which are coupled to the inner surface of the flexible shaft near the distal end thereof. The steering wires may be axially translated relative to one another by actuation of the manually actuateable steering means, which action causes the flexible shaft to bend and curve accordingly.
Also as suggested above, in conjunction with the remote status indicator of the handle, the flexible shaft further contains an electrical lead for coupling to the attachments. This electrical lead channels a signal from the attachment to the handle for indicating the status of the attachment (for example, the diametric extent to which the attachment device has expanded to open the vessel or lumen).
More particularly, with respect to the vessel and lumen expander attachment of the present invention, the attachment has several different potential embodiments, and preferred ones are disclosed herein as examples. The attachment is fitted with at least one linear drive extension, which is most simply described as a turning rod. In both embodiments, this turning rod comprises an elongate cylindrical rod having first and second elongate ends. A discontinuous threading is provided on the outer surface of the rod, and extends from a position which is a short distance from the first end to a position which is a short distance from the second end. The threading is discontinuous insofar as the threading on the upper half of the rod is directed in one direction, and the threading on the lower half is oriented in the opposing direction. A pair of nuts are mounted on the rod, a first nut being mounted on the threading of the upper half, and a second nut being mounted on the threading of the lower half. Rotation of the rod about its elongate axis, therefore, while preventing the nuts from rotating therewith, causes the nuts to either travel towards one another or apart from one another, in accordance with the direction of relative rotation and threading.
At each of the unthreaded elongate ends of the rod is also provided a circumferential recess, in which a washer is mounted. The washers are coupled to one another by elongate pins which extend in parallel with the rod. The washers are mounted to the rod such that the rod may rotate while the washers remain relatively motionless. In fact, the lower washer includes a topological feature which couples to the corresponding stability gripping feature of the flexible shaft of the electromechanical driver device such that the washers do not move relative to the driver mechanism, but such that free rotation of the rod 200 relative to them is not inhibited.
The nuts which are mounted to the rod include at least one tracking hole which mates with the pins which couple the washers together, such that they may travel linearly along the extent of the rod, but are constrained against rotation with the rod.
At the first end of the rod, the radial face of the cylinder includes a joining means (for example, a hexagonal coupling recess) for coupling to the flexible drive shaft of the electromechanical driver device. That is, when the attachment is mated to the electromechanical driver device, the rod is in mechanical communication with the flexible drive shaft such that the activation of the motor of the electromechanical driver device activates the rod, causing the nuts to travel along the rod, either toward one another, or away from one another in accordance with the specific orientations of the threading.
In a preferred embodiment, each of the two nuts are coupled to one another at a plurality of circumferential sites by means of a series of flexible joints. More particularly, each of the joints is formed by a pair of spokes, one of which is attached to the first nut at a circumferential site thereon, and the other being similarly mounted on the second nut. Each spoke is fixed at one end to its respective nut by a joint which permits the spoke to rotate radially outwardly. At the other end of each spoke, each is coupled by a similar joint to the distal end of a corresponding opposing spoke, such that the connected spokes may expand radially outwardly in an umbrella-like fashion, when the nuts are brought together, and swing radially inwardly when the nuts travel apart. It shall be understood that the spokes need not be directly coupled with one another, but instead may be coupled together by a third pin which is jointed with the distal ends of the spokes, and moves radially with respect to the rod in accordance with the motion of the nuts, but which remains parallel to the rod.
The distal ends of the spokes are also coupled with a flexible tubular material which forms a continuous expanding surface as the nuts are brought together. More particularly, the flexible tube, or shroud, includes sufficient axial rigidity (for example, by means of axial ribs), but sufficient radial expandability such that the expanding spokes create a cylindrical structure having a constant diameter and a series of radially spaced apart spokes extending from the inner surface of the flexible shroud to the central axis of the rod. In the version of this embodiment in which the spokes are separately jointed with the interior surface of the cylindrical structure, there are at least two axially separate groups of radially spaced apart spokes extending from the inner surface of the flexible shroud to the central axis of the rod. Inasmuch as the flexible shroud does not include a radially facing surface at either axial end thereof, only the rod and the spokes inhibit the free passage of fluid through the vessel as the expansion is being provided.
It shall be further understood that the invention may be constructed and coupled to the flexible drive shaft in such a way that once the attachment has been expanded to the proper amount (in an analog manner), it may be decoupled and remain as a permanent stent in the vessel or lumen. Future collapse and removal of the stent may be possible, or at least affected in a less destructive manner than other stents of the prior art, especially stents which are not collapsible.
In practice, this attachment may be utilized in the following manner. The surgeon user begins by coupling the attachment to the distal end of the flexible shaft of the electromechanical driver and making certain that the nuts have been extended to their farthest possible separation such that the flexible shroud is in its most radially compact form. The flexible shaft and attachment are then introduced into the vessel or lumen at the desired point of entry, for example into the femoral artery in the case of a blockage of a cardiovascular vessel in the vicinity of the heart. The flexible shaft and attachment are then advanced up to and through the partially occluded section of the vessel or lumen. The guidance of the flexible shaft up through the vessel or lumen is provided by remote steering wire actuation in the handle of the electromechanical driver device (as described more fully hereinabove, and in U.S. patent application Ser. No. 09/324,452, identified above). As mentioned above, this attachment, and in fact, this entire procedure is best applicable in circumstances in which the patient does not have complete blockage of the vessel, inasmuch as it is necessary to advance the attachment into the occluded section.
Once the attachment is properly positioned, the surgeon begins by actuating the finger trigger in the handle of the electromechanical driver device, causing the flexible drive shaft within the flexible shaft to rotate. The coupling of the attachment with the distal end of the flexible drive shaft causes the discontinuously threaded elongate rod to rotate (and only the discontinuously threaded elongate rod). The nuts then advance towards one another, causing the spokes to rotate outward and to radially open the flexible tube thereby pressing against the occluded vessel walls and radially opening the vessel to permit greater fluid flow. In conjunction with the versions of this embodiment in which the attachment may be remotely decoupled from the distal end of the flexible shaft of the electromechanical driver device, it may be found appropriate by the surgeon to leave the expanded stentlike structure in place to at least slow the potential re-stenosis of the vessel.